Suction structure in fixed displacement piston type compressor

ABSTRACT

A suction structure is provided for allowing refrigerant into a suction pressure region in a fixed displacement piston type compressor. The compressor includes a rotary valve. The suction structure includes a shifting device which shifts between a connecting state and a disconnecting state. The shifting device includes a valve body, a return spring, a first and a second displacement chambers, and a throttle passage. The return spring urges the valve body from a connecting position toward a disconnecting position. The volume of the first displacement chamber is displacable in accordance with an amount of a fluid inside therein. The volume of the second displacement is displaced. The fluid is filled in the first and the second displacement chambers. The throttle passage connects the first displacement chamber to the second displacement chamber. The fluid flows through the throttle passage when the volume of the first displacement chamber is displaced.

BACKGROUND OF THE INVENTION

The present invention relates to a suction structure for allowing refrigerant into a suction pressure region in a fixed displacement piston type compressor. More specifically, the compressor has a rotary valve that is integrally rotated with a rotary shaft and that has a supply passage for introducing refrigerant from the suction pressure region into a compression chamber defined in a cylinder bore by a piston.

In piston type compressors, there are two types of suction valves. One is a rotary valve as disclosed in Unexamined Japanese Patent Publications No. 7-119631 and No. 2006-083835. The other is a reed type suction valve as disclosed in Unexamined Japanese Patent Publications No. 64-088064 and No. 2000-145629. The piston type compressors including the rotary valves has lower suction resistance in introducing refrigerant into cylinder bores, and has superior energy efficiency, compared to the piston type compressors including the reed type suction valves.

At the start of the compressor disclosed in the above reference No. 7-119631, torque is rapidly increased in accordance with the compression of refrigerant gas, and is applied as a load to a vehicle engine (internal combustion). Thereby the vehicle speed is temporarily decreased at the start of the compressor, and the passengers of the vehicle feel shock.

In the piston type compressor disclosed in the above reference No. 7-119631, the rotary valve is provided so as to be axially movable in the direction of the axis of the rotary shaft. The position of the rotary valve is displaced in accordance with the pressure supplied to a control pressure chamber. A bypass groove is formed in the rotary valve so as to communicate almost all the cylinder bores to a suction port formed at the center of a cylinder block. The rotary valve is located at a position in the axial direction of the rotary shaft in such a manner that almost all the cylinder bores are communicable with the suction port through the bypass groove at the stop and at the start of the compressor. Therefore, even when the piston performs compression of the refrigerant gas in the cylinder bore at the start of the compressor, the refrigerant gas in the cylinder bore is returned to the suction port through the bypass groove. The shock at the start of the compressor does not occur, accordingly.

In order to prevent leakage of the refrigerant gas along the periphery of the rotary valve, and also to allow the rotary valve to rotate, it is required that clearance around the periphery of the rotary valve is set as small as possible However, with the structure in which the rotary valve is movable in the axial direction of the rotary shaft, the rotary valve needs clearance to allow the rotary valve to be movable in the axial direction of the rotary shaft. It is hard to set such clearance appropriately.

A compressor disclosed in Unexamined Japanese Patent Publication No. 7-139474 includes a device for decreasing load at start of the compressor. The device is located in a suction passage connected to a suction chamber. The device includes a spool valve which constitutes an oil damper. Clearance is formed between a damper portion of the spool valve and a housing. When the spool valve is moved in the direction to open the suction passage, oil in a damper chamber is gradually leaked to an intermediate chamber through the clearance. Therefore, the speed of the movement of the spool valve is gradual, and the speed of the opening of the suction passage is gradual. Thereby the shock at the start of the compressor is suppressed.

A compressor disclosed in Unexamined Japanese Patent Publication No. 2000-145629 includes a pressure differential detecting valve which is opened and closed in accordance with the pressure differential between discharge pressure and suction pressure. The pressure differential detecting valve is located between a low-pressure refrigerant passage for introducing refrigerant from the outside of the compressor and a suction chamber in the compressor. When the compressor is started in a state where the pressure in the compressor is balanced, the pressure differential detecting valve is closed, and the flow of the refrigerant from the outside of the compressor into the suction chamber is stopped. Thereby the shock at the start of the compressor is suppressed.

However, in the compressor disclosed in the reference No. 7-139474, the refrigerant is remained in the suction chamber even when the suction passage is closed by the spool valve. The residual refrigerant is introduced into the cylinder bore and compressed therein. In the compressor disclosed in the reference No. 2000-145629, the refrigerant is remained in the suction chamber even when the pressure differential detecting valve is closed. The residual refrigerant is introduced into the cylinder bore and compressed therein. The volume of the suction chamber is set large so as to suppress the suction pulsation. Thereby large amount of refrigerant is introduced into the cylinder bore in a state where the pressure differential detecting valve is closed, or the suction passage is closed, and the effect in suppressing the shock at the start of the compressor is not sufficiently obtained.

The present invention is directed to increase the effect in suppressing the shock at the start of the compressor.

SUMMARY OF THE INVENTION

In accordance with the present invention, a suction structure is provided for allowing refrigerant into a suction pressure region in a fixed displacement piston type compressor. The compressor has cylinder bores arranged around a rotary shaft for accommodating a respective piston. A cam body is formed with the rotary shaft. The piston is engaged with a cam body so that the rotation of the rotary shaft is transmitted to the piston. A compression chamber is defined by the piston in the respective cylinder bore. A rotary valve has a supply passage for introducing the refrigerant from the suction pressure region to the compression chamber. The rotary valve is rotated integrally with the rotary shaft. The suction structure includes a shifting device. The shifting device shifts between a connecting state and a disconnecting state. In the connecting state the outlet of the supply passage is connected to the suction pressure region and in the disconnecting state the outlet of the supply passage is disconnected from the suction pressure region. The shifting device includes a valve body, a return spring, a first and a second displacement chambers, and a throttle passage. The valve body is movable between the connecting position and the disconnecting position. The connecting position corresponds to the connecting state and the disconnecting position corresponds to the disconnecting state. The return spring urges the valve body from a connecting position toward a disconnecting position. The first displacement chamber urges the valve body from the disconnecting position to the connecting position. The volume of the first displacement chamber is displacable in accordance with an amount of a fluid inside therein. The volume of the second displacement chamber is displacable. The fluid is filled in the first and the second displacement chambers. The throttle passage connects the first displacement chamber to the second displacement chamber. The volume of the first displacement chamber is increased when the fluid flows from the second displacement chamber to the first displacement chamber through the throttle passage. The volume of the first displacement chamber is decreased when the fluid flows from the first displacement chamber to the second displacement chamber through the throttle passage.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

FIG. 1 is a longitudinal cross-sectional view of a compressor according to a first preferred embodiment of the present invention;

FIG. 2A is a cross-sectional view which is taken along the line I-I in FIG. 1;

FIG. 2B is a cross-sectional view which is taken along the line II-II in FIG. 1;

FIG. 3 is a partially enlarged cross-sectional view illustrating the suction structure of the compressor in a disconnecting state according to the first preferred embodiment of the present invention;

FIG. 4 is a partially enlarged cross-sectional view illustrating the suction structure of the compressor in a connecting state according to the first preferred embodiment of the present invention;

FIG. 5A is a partially enlarged cross-sectional view of the compressor illustrating a suction structure in a disconnecting state according to a second preferred embodiment of the present invention;

FIG. 5B is a partially enlarged cross-sectional view of a compressor illustrating the suction structure in a connecting state according to the second preferred embodiment of the present invention;

FIG. 6 is a longitudinal cross-sectional view of a compressor illustrating a suction structure in a connecting state according to a third preferred embodiment of the present invention;

FIG. 7 is a longitudinal cross-sectional view of the compressor illustrating the suction structure in a disconnecting state according to the third preferred embodiment of the present invention;

FIG. 8A is a partially enlarged cross-sectional view of a compressor illustrating the suction structure in a disconnecting state according to a fourth preferred embodiment of the present invention;

FIG. 8B is a partially enlarged cross-sectional view of a compressor illustrating the suction structure in a connecting state according to the fourth preferred embodiment of the present invention;

FIG. 9A is a partially enlarged cross-sectional view of a compressor illustrating the suction structure in a connecting state according to a fifth preferred embodiment of the present invention;

FIG. 9B is a partially enlarged cross-sectional view of a compressor illustrating the suction structure in a disconnecting state according to the fifth preferred embodiment of the present invention; and

FIG. 10 is a longitudinal cross-sectional view of a compressor according to a sixth preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first preferred embodiment of the present invention will now be described with reference to FIGS. 1 through 4. It is noted that the front side and the rear side of a fixed displacement piston type compressor 10 respectively correspond to the left side and the right side in the drawings. Referring to FIG. 1, a front cylinder block 11 is connected to a rear cylinder block 12. A front housing 13 is connected to the front cylinder block 11. A rear housing 14 is connected to the rear cylinder block 12. The front and rear cylinder blocks 11, 12 and the front and rear housings 13, 14 constitute a whole compressor housing assembly of the fixed displacement piston type compressor 10. A discharge chamber 131 as a discharge pressure region in the compressor 10 is defined in the front housing 13. A discharge chamber 141 as a discharge pressure region in the compressor 10 is defined in the rear housing 14. A suction chamber 142 as a suction pressure region is defined in the rear housing 14. It is noted that “in the compressor” corresponds to the inside of the whole compressor housing assembly, and that “out of the compressor” corresponds to the outside of the whole compressor housing assembly.

A valve port plate 15, a valve plate 16 and a retainer plate 17 are interposed between the front cylinder block 11 and the front housing 13. A valve port plate 18, a valve plate 19 and a retainer plate 20 are interposed between the rear cylinder block 12 and the rear housing 14. Discharge ports 151, 181 are respectively formed in the valve port plates 15, 18. Discharge valves 161, 191 are respectively formed in the valve plates 16, 19 to open and close the respective discharge ports 151, 181. Retainers 171, 201 are respectively formed in the retainer plates 17, 20 to regulate the respective opening degrees of the discharge valves 161, 191.

A rotary shaft 21 is rotatably supported by the front and rear cylinder blocks 11, 12 and is inserted into shaft holes 111, 121 which extend through the front and rear cylinder blocks 11, 12. The outer periphery of the rotary shaft 21 is in contact with the inner periphery of the shaft holes 111, 121. The rotary shaft 21 is directly supported by the front and rear cylinder blocks 11, 12 through the inner periphery of the respective shaft holes 111 and 121. A contacting portion of the outer periphery of the rotary shaft 21 with the shaft hole 111 forms a sealing circumferential surface 211. A contacting portion of the outer periphery of the rotary shaft 21 with the shaft hole 121 forms a sealing circumferential surface 212.

A swash plate 23 as a cam body is secured to the rotary shaft 21. The swash plate 23 is accommodated in a crank chamber 24 which is defined between the front and rear cylinder blocks 11, 12. A lip-seal type shaft seal member 22 is interposed between the front housing 13 and the rotary shaft 21. The shaft seal member 22 prevents leakage of the refrigerant gas through the clearance between the front housing 13 and rotary shaft 21. The front end of the rotary shaft 21 protruding externally from the front housing 13 is connected to a vehicle engine 26 as an external drive source through an electromagnetic clutch 25. The rotary shaft 21 receives driving force for rotation from the vehicle engine 26 through the electromagnetic clutch 25.

As shown in FIG. 2A, a plurality of front cylinder bores 27 is formed in the front cylinder block 11 and is arranged around the rotary shaft 21. As shown in FIG. 2B, a plurality of rear cylinder bores 28 is formed in the rear cylinder block 12 and is arranged around the rotary shaft 21. Front and rear heads of a double-headed piston 29 are respectively accommodated in the pair of the cylinder bores 27, 28.

As shown in FIG. 1, the double-headed piston 29 is engaged with the swash plate 23 through a pair of shoes 30. The swash plate 23 integrally rotates with the rotary shaft 21. The rotary motion of the swash plate 23 is transmitted to the double-headed piston 29 through the shoes 30 so that the double-headed piston 29 reciprocates in the pair of the cylinder bores 27, 28. Compression chambers 271, 281 are defined in the respective cylinder bores 27, 28.

An in-shaft passage 31 is formed in the rotary shaft 21. The in-shaft passage 31 extends along the rotary axis 210 of the rotary shaft 21. An inlet 311 of the in-shaft passage 31 is formed at an end surface 213 of the rotary shaft 21 in the cylinder block 12. The inlet 311 is open to the suction chamber 142 in the rear housing 14. A front outlet 312 of the in-shaft passage 31 is open at the front sealing circumferential surface 211 of the rotary shaft 21 in the shaft hole 111. A rear outlet 313 of the in-shaft passage 31 is open at the rear sealing circumferential surface 212 of the rotary shaft 21 in the shaft hole 121.

As shown in FIG. 2A, a front communication passage 32 is formed in the front cylinder block 11 so as to communicate with the cylinder bore 27 and the shaft hole 111. As shown in FIG. 2B, a rear communication passage 33 is formed in the rear cylinder block 12 so as to communicate with the cylinder bore 28 and the shaft hole 121. As the rotary shaft 21 rotates, the outlets 312, 313 of the in-shaft passage 31 intermittently communicates with the communication passages 32, 33.

When the front cylinder bore 27 is in a suction cycle, that is, when the double-headed piston 29 moves from the left side to the right side in FIG. 1, the outlet 312 communicates with the communication passage 32. As a result, refrigerant in the in-shaft passage 31 is introduced into the compression chamber 271 in the cylinder bore 27 through the outlet 312 and the communication passage 32.

When the front cylinder bore 27 is in a discharge cycle, that is, when the double-headed piston 29 moves from the right side to the left side in FIG. 1, the outlet 312 is disconnected from the communication passage 32. As a result, refrigerant in the compression chamber 271 is discharged to the discharge chamber 131 through the discharge port 151 by pushing the discharge valve 161 away. The refrigerant discharged to the discharge chamber 131 flows out to an external refrigerant circuit 34 through a passage 341.

When the rear cylinder bore 28 is in a suction cycle, that is, when the double-headed piston 29 moves from the right side to the left side in FIG. 1, the outlet 313 communicates with the communication passage 33. As a result, refrigerant in the in-shaft passage 31 of the rotary shaft 21 is introduced into the compression chamber 281 of the cylinder bore 28 through the outlet 313 and the communication passage 33.

When the rear cylinder bore 28 is in a discharge cycle, that is, when the double-headed piston 29 moves from the left side to the right side in FIG. 1, the outlet 313 is disconnected from the communication passage 33. As a result, refrigerant in the compression chamber 281 is discharged to the discharge chamber 141 through the discharge port 181 by pushing the discharge valve 191 away. The refrigerant discharged to the discharge chamber 141 flows out to the external refrigerant circuit 34 through a passage 342.

The external refrigerant circuit 34 is provided with a heat exchanger 37 for removing heat from refrigerant, an expansion valve 38, and a heat exchanger 39 for evaporating refrigerant with heat. The expansion valve 38 controls the flow rate of refrigerant in accordance with the fluctuation in temperature of the gaseous refrigerant at the outlet of the heat exchanger 39. The refrigerant flowing out to the external refrigerant circuit 34 returns to the suction chamber 142.

The part of the rotary shaft 21 corresponding to the sealing circumferential surface 211 forms a first rotary valve 35. The part of the rotary shaft 21 corresponding to the sealing circumferential surface 212 forms a second rotary valve 36. The rotary valves 35, 36 are formed integrally with the rotary shaft 21. That is, the rotary shaft 21 serves as rotary valves. The rotary axis 210 serves as the rotary axis of the rotary valves. The end surface 213 of the rotary shaft 21 (the end surface of the rotary valve) intersects with the rotary axis 210 of the rotary valve. The in-shaft passage 31 and outlets 312, 313 form the supply passage of the rotary valves 35, 36. The shaft hole 111 serves as the valve accommodation chamber for accommodating the first rotary valve 35, and the shaft hole 121 serves as the valve accommodation chamber for accommodating the second rotary valve 36.

As shown in FIGS. 3 and 4, a base portion 40 is formed integrally with the end wall of the rear housing 14. An inner wall of the rear housing 14 defines the suction chamber 142. A cylindrical portion 41 is formed integrally with the inner wall surface of the base portion 40. A valve body 42 in the form of a spool is slidably inserted in the inner space 411 inside of the cylindrical portion 41. The valve body 42 includes a disk-like piston member 43 and a cylindrical member 44. An introduction port 441 is open at the outer peripheral surface of the cylindrical member 44. The introduction port 441 communicates with the inner space 442 inside of the cylindrical member 44. The inner space 442 serves as an inner passage of the valve body 42. The piston member 43 defines a first pressure chamber 412 in the inner space 411 inside of the cylindrical portion 41.

A guide cylinder 45 is formed integrally with the end surface of the rear cylinder block 12 adjacent to the rear housing 14. The inner space 451 of the guide cylinder 45 communicates with the inlet 311 of the in-shaft passage 31 of the rotary shaft 21. The rear end of the guide cylinder 45 and the front end of the cylindrical portion 41 is spaced apart from each other, and the cylindrical member 44 of the valve body 42 is slidably fitted together by insertion with the guide cylinder 45. A circular clip 46 is attached to the inner circumferential surface of the guide cylinder 45. A return spring 47 is interposed between the circular clip 46 and the piston member 43. The return spring 47 urges the valve body 42 so that the valve body 42 approaches the base portion 40. When the valve body 42 approaches the base portion 40, the volume of the first pressure chamber 412 decreases.

In the state shown in FIG. 4, the introduction port 441 is in a position where the entire introduction port 441 is exposed to the suction chamber 142. The in-shaft passage 31 communicates with the suction chamber 142 through the inner space 451 of the guide cylinder 45, the inner space 442 of the cylindrical portion 44 and the introduction port 441. In the state shown in FIGL 3, the introduction port 441 is in a position where the entire introduction port 441 is fitted in the inner space 411, and the in-shaft passage 31 is disconnected from the suction chamber 142. FIG. 4 shows a state where the valve body 42 is in a position to connect the in-shaft passage 31 to the suction chamber 142. FIGL 3 shows a state where the valve body 42 is in a position to disconnect the in-shaft passage 31 from the suction chamber 142.

As shown in FIGS. 3 and 4, a recess 401 is formed in the rear end surface of the base portion 40. A partition plate 48 as a partition wall is accommodated in the recess 401. A cylindrical cover 49 with a bottom is fixedly jointed to the rear end surface of the base portion 40 by fastening with a screw 50. The cover 49 presses the partition plate 48 to the bottom of the recess 401 by fastening with the screw 50.

A through hole 55 is formed at the bottom of the recess 401 so as to communicate with the first pressure chamber 412. A first bellows 51 is connected to the front surface 56 of the partition plate 48 which faces the through hole 55. A first movable end 512 of the first bellows 51 is fixed to the piston member 43 of the valve body 42, thereby the valve body 42 and the first movable end 512 of the first bellows 51 are integrally movable. The first bellows 51 is extended and contracted in the direction of the rotary axis 210 of the rotary shaft 21. The first bellows 51 defines a first displacement chamber 511 in the first pressure chamber 412 and the through hole 55. The first bellows 51 serves as a first chamber forming member, and the first movable end 512 serves as a first movable portion. The first displacement chamber 511 serves to urge the valve body 42 from the disconnecting position as shown in FIG. 3 toward the connecting position as shown in FIG. 4. The volume of the first displacement chamber 511 is displaced in accordance with the displacement of the position of the first movable end 512 (the position displacement in the direction of the rotary axis 210). That is, the first displacement chamber 511 formed between the partition plate 48 and the first movable end 512 changes the volume in accordance with the position displacement of the valve body 42.

A second bellows 52 is located in the inner space 491 of the cover 49. The second bellows 52 is connected to the rear surface 57 of the partition plate 48. The second bellows 52 is extended and contracted in the direction of the rotary axis 210 of the rotary shaft 21. The second bellows 52 defines a second displacement chamber 521 in the inner space 491. The second displacement chamber 521 is formed between the partition plate 48 and a second movable end 522. The second bellows 52 serves as a second chamber forming member. The volume of the second displacement chamber 521 is displaced in accordance with the position displacement of the second movable end 522 (the position displacement in the direction of the rotary axis 210).

When the volume displacement variation in the first displacement chamber 511 is the same magnitude as that of the second displacement chamber 521, the stroke length of the first movable end 512 of the first bellows 51 is greater than that of the second movable end 522 of the second bellows 52. That is, the stroke length of the first movable end 512 is greater than the stroke length of the second movable end 522, when the volume displacement variation inside of the bellows 51, 52 increases or decreases by the same magnitude.

A throttle passage 53 is formed to extend through the partition plate 48 so that the throttle passage 53 communicates with the first and the second displacement chambers 511, 521. Oil (liquid as a fluid) is filled in the first and the second displacement chambers 511, 521 and the throttle passage 53.

A groove 561 is formed in the inner surface 56 of the partition plate 48. A passage 54 is formed through the base portion 40. The through hole 55 communicates with the suction chamber 142 through the groove 561 and the passage 54. Thereby the pressure in the suction chamber 142 is applied to the first pressure chamber 412. The pressure in the first pressure chamber 412 opposes to the pressure in the inner space 442 through the valve body 42.

A groove 571 is formed in the outer surface 57 of the partition plate 48. The inner space 491 communicates with the suction chamber 142 through the groove 571 and the passage 54. The pressure in the suction chamber 142 is applied to the inner space 491. The inner space 491 is denoted as the second pressure chamber 491.

As shown in FIG. 1, the excitation of the electromagnetic clutch 25 is controlled by a computer C. The computer C is connected by way of signals to an operation switch 58 for an air conditioner, a room temperature setting device 59 for setting a target room temperature, and a room temperature detecting device 60 for detecting a room temperature. When the operation switch 58 is on, the computer C controls the electric supply to the electromagnetic clutch 25 in accordance with the temperature difference between the target room temperature and the detected room temperature.

The computer C shuts off the electric supply to the electromagnetic clutch 25, when the detected temperature is lower than the target temperature, or, when the detected temperature is higher than the target temperature and the temperature difference is within an allowable range. In this case, the electromagnetic clutch 25 is in a disconnected state, and the driving force of the vehicle engine 26 is not transmitted to the rotary shaft 21. The computer C supplies electricity to the electromagnetic clutch 25, when the detected temperature is higher than the target temperature and the temperature difference between the detected temperature and the target temperature is beyond the allowable level. In this case, the electromagnetic clutch 25 is in a connected state, and the driving force of the vehicle engine 26 is transmitted to the rotary shaft 21.

When the operation of the fixed displacement piston type compressor 10 is shut down (the electromagnetic clutch 25 is disconnected), the pressure in the compressor 10 is balanced. In this state, the valve body 42 is in the disconnecting position by the spring force of the return spring 47, as shown in FIG. 3. When the fixed displacement piston type compressor 10 is started, the refrigerant in the in-shaft passage 31 and the inner spaces 451, 442 is introduced into the compression chambers 271 (as shown in FIG. 1) and 281. Due to the suction motion, the pressure in the in-shaft passage 31 and the inner spaces 451, 442 is decreased. That is, the pressure in the in-shaft passage 31 and the inner spaces 451, 442 becomes lower than the pressure in the suction chamber 142. The pressure in the suction chamber 142 is applied to the first pressure chamber 412 and the second pressure chamber 491. The pressure in the first and the second pressure chambers 412, 491 corresponds to the pressure in the suction chamber 142. The pressure in the first pressure chamber 412 opposes to the pressure in the inner spaces 451, 442 and the spring force of the return spring 47 through the valve body 42. The second pressure chamber 491 opposes to the pressure in the inner spaces 451, 442 and the spring force of the return spring 47 through the oil in the displacement chambers 521, 511 and the valve body 42.

The spring force of the return spring 47 is set in such a manner that the pressure difference between the pressure chambers 412, 491 and the inner spaces 451, 442 overcomes the spring force of the return spring 47, when the compressor 10 is operated. Thereby the valve body 42 is moved from the disconnecting position as shown in FIG. 3 to the connecting position as shown in FIG. 4. The first movable end 512 of the first bellows 51 is moved integrally with the valve body 42, and the first bellows 51 is extended so as to increase the volume of the first displacement chamber 511. In accordance with the increase in volume of the first displacement chamber 511, the oil in the second displacement chamber 521 flows into the first displacement chamber 511 through the throttle passage 53.

When the operation of the compressor 10 is stopped, the refrigerant in the in-shaft passage 31 and the inner spaces 451, 442 is not introduced into the compression chambers 271 (as shown in FIG. 1)) and 281. Thereby the pressure in the in-shaft passage 31 and the inner spaces 451, 442 is increased. Therefore, the pressure in the in-shaft passage 31 and the inner spaces 451, 442 is balanced with the pressure in the pressure chambers 412, 491. Thereby the valve body 42 is moved from the connecting position as shown in FIG. 4 to the disconnecting position as shown in FIG. 3 due to the spring force of the return spring 47.

The valve body 42 is shifted between the connecting position and the disconnecting position in accordance with the pressure in the supply passage (the in-shaft passage 31) which corresponds to the operated state and the stopped state of the compressor 10. When the valve body 42 is located in the connecting position, the outlets 312, 313 of the in-shaft passage 31 are connected to the suction chamber 142 (suction pressure region) in the compressor 10. When the valve body 42 is located in the disconnecting position, the outlets 312, 313 of the in-shaft passage 31 are disconnected from the suction chamber 142. The valve body 42, the return spring 47, the partition plate 48, the first bellows 51, the second bellows 52, and the throttle passage 53 constitute a shifting device 61. The shifting device 61 shifts between the connecting position and the disconnecting position. The valve body 42, the first bellows 51, the partition plate 48, and the second bellows 52 are aligned in this order in series from the side of the rotary shaft 21 to side of the cover 49.

In the state shown in FIG. 3, the shifting device 61 is in the disconnecting state where the outlets 312 (as shown in FIG. 1) and 313 of the in-shaft passage 31 are disconnected from the suction chamber 142. In the state shown in FIG. 4, the shifting device 61 is in the connecting state where the outlets 312 (as shown in FIG. 1) and 313 of the in-shaft passage 31 are connected to the suction chamber 142.

According to the first preferred embodiment, the following advantageous effects are obtained.

(1) When the compressor 10 is started, the pressure in the in-shaft passage 31 and the inner spaces 451, 442 is decreased, and the valve body 42 is moved from the disconnecting position to the connecting position. In this case, the part of the introduction port 441 exposing to the suction chamber 142 is increased. That is, the cross-sectional area of the introduction port 441 for connecting the inner space 442 to the suction chamber 142 to is increased.

When the valve body 42 is moved from the disconnecting position to the connecting position, the volume of the first displacement chamber 511 is increased. Thereby the oil in the second displacement chamber 521 flows into the first displacement chamber 511 through the throttle passage 53, and the volume of the second displacement chamber 521 is decreased. The oil flowing through the throttle passage 53 generates flow resistance by the throttling effect of the throttle passage 53. Due to the flow resistance, the volume displacement variation of the first and the second displacement chambers 511, 521 is delayed and the movement of the valve body 42 is damped. That is, the movement speed of the valve body 42 is slowed down. Therefore, the increase variation in the cross-sectional area of the introduction port 441 between the suction chamber 142 and the inner space 442 is reduced to a lower level, and the sudden flow of the refrigerant from the suction chamber 142 into the inner space 442 is prevented. As a result, the shock at the start of the compressor 10 is suppressed.

Additionally, the above structure reduces the amount of the refrigerant which is compressed during the time when the suction chamber 142 is disconnected from the introduction port 441. Thereby the fluctuation in torque, or the shock at the start of the compressor 10 is effectively suppressed.

(2) When the compressor 10 is stopped, the valve body 42 is returned to the disconnecting position by the spring force of the return spring 47. Utilizing the return spring 47 is effective in returning the valve body 42 to the disconnecting position with a simple construction. (3) The oil is an appropriate fluid in delaying the movement speed of the valve body 42 by Increasing the flow resistance in the throttle passage 53. (4) The bellows 51, 52 are appropriate for preventing the oil leakage from the first and the second displacement chambers 511, 521. (5) When the valve body 42 is moved from the disconnecting position shown in FIG. 3 to the connecting position shown in FIG. 4, the cross-sectional area of the introduction port 441 increases and reaches a predetermined value. Therefore, the greater the stroke length of the valve body 42 is, the more the increase variation rate of the cross-sectional area of the introduction port 441 between the suction chamber 142 and the inner space 442 is suppressed. That is, it is effective to set a greater stroke length of the valve body 42 in increasing the effect of suppressing the shock at the start of the compressor 10.

The stroke length of the first movable end 512 of the first bellows 51 is set greater than that of the second movable end 522 of the second bellows 52 in case the volume displacement variation of the first bellows 51 is the same as that of the second bellows 52. Such a construction is appropriate for obtaining a greater stroke length of the valve body 42 while downsizing the cover 49 (downsizing in the direction of the rotary axis 210)

(6) The introduction port 441 as the inlet for the inner space 442 of the valve body 42 is located in the inner space 411 so as to be closed when the valve body 42 is in the disconnecting position. The introduction port 441 is exposed to the suction chamber 142 at the outside of the inner space 411, when the valve body 42 is in the connecting position. The construction in which the introduction port 441 is moved into and away from the inner space 411 is appropriate for ensuring a sufficient cross-sectional area in the supply passage by enlarging the introduction port 441.

A second preferred embodiment of the present invention will now be described with reference to FIGS. 5A, 5B. The same reference numerals denote the identical components to those in the first preferred embodiment.

The rear housing 14 includes a communication chamber 62 and a valve hole 631 formed therein. A plate 64 for opening and closing the valve hole 631 is accommodated in the communication chamber 62. The valve hole 631 is formed through a partition wall 63 which separates the communication chamber 62 from the suction chamber 142. The inlet 311 of the in-shaft passage 31 is formed at the rear end surface 213 of the rotary shaft 21 in the rear cylinder block 12 and is open to the communication chamber 62 in the rear housing 14.

A piston 65 is inserted in the inner space 411. A rod 66 is formed integrally with the piston 65. The plate 64 is fixed to the end of the rod 66. A planar valve seat 632 is formed in the surface of the partition wall 63 adjacent to the communication chamber 62. The plate 64 comes into contact with the valve seat 632 for closing the valve hole 631, and moved apart from the valve seat 632 for opening the valve hole 631. A sealing surface 641 of the plate 64 facing the valve seat 632 is formed of a planar shape. In other words, when the valve hole 631 is closed by the plate 64, the sealing surface 641 of the plate 64 is in surface contact with the valve seat 632. The piston 65, the rod 66 and the plate 64 constitute a valve body 67 for opening and closing the valve hole 631. The valve body 67 defines a first displacement chamber 413 in the inner space 411. The first displacement chamber 413 communicates with the second displacement chamber 521 through the throttle passage 53.

The first displacement chamber 413 is defined by the piston 65 as a first chamber forming member. The volume of the first displacement chamber 413 is displaced in accordance with the position displacement of the piston 65 as a first movable portion (the position displacement in the direction of the rotary axis 210). That is, the volume of the first displacement chamber 413 is displaced in accordance with the position displacement of the valve body 67 (the position displacement in the direction of the rotary axis 210).

A return spring 68 is interposed between the piston 65 and the partition wall 63. The return spring 68 urges the piston 65 in the direction to push the piston 65 into the inner space 411. In FIG. 5B, the valve body 67 is in the connecting position connecting the communication chamber 62 to the suction chamber 142 by opening the valve hole 631. In FIG. 5A, the valve body 67 is in a disconnecting position disconnecting the communication chamber 62 from the suction chamber 142 by closing the valve hole 631. The return spring 68 urges the valve body 67 in the direction from the connecting position toward the disconnecting position.

Plural restricting members 642 protrude from the front surface of the plate 64 facing the end surface 213 of the rotary shaft 21. The restricting members 642 come into contact with the rear end of a cylindrical portion 123 protruding from an end surface 122 of the rear cylinder block 12, and are moved away from the rear end of the cylindrical portion 123. In a state where the valve body 67 is in the connecting position as shown in FIG. 5B, the restricting members 642 are in contact with the rear end of the cylindrical portion 123. In a state where the valve body 67 is in the disconnecting position as shown in FIG. 5A, the restricting members 642 are spaced apart from the rear end of the cylindrical portion 123.

When the operation of the compressor 10 is stopped, the valve body 67 is located in the disconnecting position as shown in FIG. 5A due to the spring force of the return spring 68. In this state, the refrigerant in the suction chamber 142 does not flow into the communication chamber 62. When the compressor 10 is started, the refrigerant in the in-shaft passage 31 and the communication chamber 62 is introduced into the compression chambers 271 (shown in FIG. 1) and 281. Due to the suction cycle, the pressure in the in-shaft passage 31 and the communication chamber 62 decreases. That is, the pressure in the in-shaft passage 31 and the communication chamber 62 becomes lower than the pressure in the suction chamber 142. Thereby the valve body 67 is in the connecting position as shown in FIG. 5B, and the refrigerant in the suction chamber 142 flows into the compression chamber 271 (as shown in FIG. 1) and 281 through the valve hole 631, the communication chamber 62 and the in-shaft passage 31.

The valve body 67, the return spring 68, the partition wall 63, the bellows 52, and the throttle passage 53 constitute a shifting device 61A. The shifting device 61A shifts between the connecting state and the disconnecting state. In the connecting state, the outlets 312, 313 of the supply passage are connected to the suction chamber 142 (the suction pressure region). In the disconnecting state, the outlets 312, 313 of the supply passage are disconnected from the suction chamber 142.

Similar to the first embodiment, a shock absorbing effect at the start of the compressor 10 is obtained in the second preferred embodiment. Further, the volume of the communication chamber 62 which accommodates the plate 64 is reduced, and the shock absorbing effect is higher.

The following will describe a third embodiment of the present invention with reference to FIGS. 6 and 7. The same reference numerals denote the identical components to those in the second preferred embodiment.

A piston 69 is slidably fitted in the cylindrical portion 41. The first movable end 512 of the first bellows 51 is fixed to the piston 69. The piston 69 defines the first pressure chamber 412 in the inner space 411.

A rod 70 is connected to the piston 69. The rod 70 is inserted in an in-shaft passage 31A. The in-shaft passage 31A includes a small-diameter passage 314 and a large-diameter passage 315. A disk 71 is fixed to the front end of the rod 70 in the small-diameter passage 314. A cylindrical body 72 with a circular cross-section is fixed to the rod 70 in the large-diameter passage 315.

The disk 71 is fitted in the small-diameter passage 314 in such a manner that the disk 71 is slidable in the direction of the rotary axis 210 of the rotary shaft 21. The cylindrical body 72 is fitted in the large-diameter passage 315 in such a manner that the cylindrical body 72 is slidable in the direction of the rotary axis 210 of the rotary shaft 21, and that the outlet 313 is to be opened and closed, Part of the in-shaft passage 31A between the disk 71 and the cylindrical body 72 communicates with part of the in-shaft passage 31A between the inlet 311 and the cylindrical body 72 through inner space of the cylindrical body 72.

As shown in FIG. 7, when the cylindrical body 72 is in a position to close the outlet 313, the disk 71 is located at the upstream of the outlet 312 in the in-shaft passage 31A. In this state, the refrigerant in the in-shaft passage 31A does not flow into the compression chamber 271 through the outlet 312. As shown in FIG. 6, when the cylindrical body 72 is in a position to open the outlet 313, the disk 71 is located at the downstream of the outlet 312 in the in-shaft passage 31A. In this state, the refrigerant in the in-shaft passage 31A flows into the compression chamber 271 through the outlet 312.

A step 316 is formed between the small-diameter passage 314 and the large-diameter passage 315. A return spring 73 is interposed between the step 316 and the cylindrical body 72. The return spring 73 urges the disk 71, the cylindrical body 72, the rod 70 and the piston 69 altogether in the direction toward the first pressure chamber 412 so as to push the piston 69 into the inner space 411.

When the operation of the compressor 10 is stopped, the disk 71 and the cylindrical body 72 are maintained at the disconnecting position as shown in FIG. 7 by the spring force of the return spring 73. When the compressor 10 is started, the refrigerant in a space 317 (a part of the in-shaft passage 31A) defined by the disk 71 and the end of the in-shaft passage 31A is introduced into the compression chamber 271, and the pressure in the space 317 decreases. Thereby, the disk 71 and the cylindrical body 72 are moved from the disconnecting position as shown in FIG. 7 toward the connecting position as shown in FIG. 6 to overcome the spring force of the spring 73. When the compressor 10 is stopped, the disk 71 and the cylindrical body 72 are returned to the disconnecting position as shown in FIG. 7 by the spring force of the return spring 73. The disk 71, the cylindrical body 72, the rod 70 and the piston 69 constitute a valve body which defines the first pressure chamber 412 in the inner space 411.

The valve body is shifted between the connecting position and the disconnecting position in accordance with the pressure in the space 317 (a part of the in-shaft passage 31A) which corresponds to the operated state and stopped state of the compressor 10. In the connecting position, the outlets 312, 313 of the supply passage are connected to the suction chamber 142 (the suction pressure region) in the compressor 10. In the disconnecting position, the outlets 312, 313 of the supply passage are disconnected from the suction chamber 142. The valve body, the partition wall 48, the first bellows 51, the second bellows 52, and the throttle passage 53 constitute a shifting device 61B. The shifting device 61B shifts between the connecting state and the disconnecting state. In the connecting state, the outlets 312, 313 of the supply passage are connected to the suction chamber 142 (suction pressure region). In the disconnecting state, the outlets 312, 313 of the supply passage are disconnected from the suction chamber 142.

According to the third preferred embodiment, the similar effects as the second preferred embodiment are obtained. Specifically, the third embodiment is more effective than the first and the second embodiments in absorbing the shock at the start of the compressor 10. That is because the refrigerant which is to be introduced into the compression chambers 271, 281 is only in the space 317, outlets 312, 313, communication passages 32, 33, when the disk 71 and the cylindrical body 72 are in the disconnecting position.

When the piston 69 and the rod 70 are formed to be rotatable with respect to each other, the mutual rotation between the return spring 73 and the rotary shaft 21 is prevented. The frictional damage of the return spring 73 and the rotary shaft 21 due to the mutual rotation therebetween is prevented, accordingly. Alternatively, the cylindrical body 72 and the return spring 73 may be constructed so as to be relatively rotated.

The following will describe a fourth preferred embodiment of the present invention with reference to FIGS. 8A, 8B. The same reference numerals denote the identical components to those in the third preferred embodiment.

The piston 69 is fitted in the inner space 411. The piston 69 serves as the first chamber forming member, and the first displacement chamber 413 is defined by the piston 69 in the inner space 411. The volume of the first displacement chamber 413 is displaced in accordance with the position displacement of the piston 69 as the first movable portion (the position displacement in the direction of the rotary axis 210).

The first displacement chamber 413 communicates with the second displacement chamber 521 through the throttle passage 53. The stroke length of the piston 69 is set greater than that of the second movable end 522 of the second bellows 52 when the volume displacement variation of the first displacement chamber 413 is the same magnitude as that of the second displacement chamber 521.

When the compressor 10 is in the stopped state, the cylindrical body 72 is retained in a disconnecting position as shown in FIG. 8A by the spring force of the return spring 73. When the compressor 10 is started, the cylindrical body 72 is shifted from a disconnecting position as shown in FIG. 8A to a connecting position as shown in FIG. 8B by overcoming the spring force of the return spring 73. The disk 71, the cylindrical body 72, the rod 70, and the piston 69 constitute a valve body. The valve body defines the first displacement chamber 413 in the inner space 411. The valve body, the partition wall 48, the bellows 52, and the throttle passage 53 constitute a shifting device 61C which shifts between the connecting state and the disconnecting state. In the connecting state, the outlets 312, 313 of the supply passage are connected to the suction chamber 142 (the suction pressure region). In the disconnecting state, the outlets 312, 313 of the supply passage are disconnected from the suction chamber 142.

According to the fourth preferred embodiment, the similar effects are obtained as the third preferred embodiment.

The following will describe a fifth preferred embodiment of the present invention with reference to FIGS. 9A, 9B. The same reference numerals denote the identical components to those in the fourth preferred embodiment.

A cylinder 75 is connected to the piston 69 so as to be relatively rotatable. The cylinder 75 is slidably fitted into the in-shaft passage 31A. A front end wall 752 is formed at the front end of the cylinder 75. A square pin 76 is fixed to the closed end of the in-shaft passage 31A. The square pin 76 is relatively slidably inserted through the end wall 752 of the cylinder 75. The cylinder 75 is rotated integrally with the rotary shaft 21. The cylinder 75 and the square pin 76 are slidable in the in-shaft passage 31A in the state where the square pin 76 is inserted through the end wall 752. The piston 69 and the cylinder 75 constitute a valve body which defines the first displacement chamber 413 in the inner space 411.

The cylinder 75 has a small-diameter cylinder portion 77 and a large-diameter cylinder portion 78. The small-diameter cylinder portion 77 is fitted in the small-diameter passage 314. The large-diameter cylinder portion 78 is fitted in the large-diameter passage 315. An introduction port 751 is formed in the large-diameter cylinder portion 78 in the suction chamber 142 so as to interconnect the suction chamber 142 and an inner space 750. A step 753 is formed between the small-diameter cylinder portion 77 and the large-diameter cylinder portion 78. A return spring 74 is interposed between the step 753 formed in the cylinder 75 and the step 316 formed in the rotary shaft 21. The return spring 74 urges the cylinder 75 so as to push the piston 69 into the inner space 411 in the direction toward the partition wall 48.

A through hole 771 is formed in the small-diameter cylinder portion 77 in the small-diameter passage 314 so as to communicate with the inside of the small-diameter cylinder portion 77. A through hole 781 is formed in the large-diameter cylinder portion 78 so as to communicate with the inside of the large-diameter cylinder portion 78.

A piston 79 is slidably accommodated in a second pressure chamber 491. The piston 79 serves as a second chamber forming member and defines a second displacement chamber 492 in the second pressure chamber 491. The volume of the second displacement chamber 492 is displaced in accordance with the position displacement of the piston 79 as a second movable portion. That is, the volume in the first displacement chamber 413 is displaced in accordance with the position displacement of the valve body (the position displacement in the direction of the rotary axis 210) which defines the first displacement chamber 413.

The second displacement chamber 492 communicates with the first displacement chamber 413 through the throttle passage 53. The second pressure chamber 491 communicates with the suction chamber 142 through a passage 80. The diameter of the piston 79 is larger than the that of the piston 69. Therefore, the stroke length of the piston 69 is greater than that of the piston 79 when the volume displacement variation of the first displacement chamber 413 is the same magnitude as that of the second displacement chamber 492.

The valve body which defines the first displacement chamber 413 in the inner space 411, the partition wall 48, the throttle passage 53, and the piston 79 constitute a shifting device 61D. The shifting device 61D shifts between the connecting state and the disconnecting state. In the connecting state, the outlets 312, 313 of the supply passage is connected to the suction chamber 142 (the suction pressure region) in the compressor 10. In the disconnecting state, the outlets 312, 313 of the supply passage is disconnected from the suction chamber 142.

FIG. 9B shows a state where the small-diameter cylinder portion 77 as the valve body closes the outlet 312 and the large-diameter cylinder portion 78 as the valve body closes the outlet 313. Thereby the outlets 312, 313 are disconnected from the inner space 750 in the cylinder 75. FIG. 9A shows a state where the through hole 771 of the small-diameter cylinder portion 77 is connected to the outlet 312 and the through hole 781 of the large-diameter portion 78 is connected to the outlet 313. In this state, the outlets 312, 313 communicate with the inner space 750. The refrigerant in the suction chamber 142 is to flow into the compression chamber 271 through the introduction port 751, the inner space 750, the through hole 771, the outlet 312, and the communication passage 32. The refrigerant in the suction chamber 142 is to flow into the compression chamber 281 through the introduction port 751, the inner space 750, the through hole 781, the outlet 313, and the communication passage 33.

As shown in FIG. 9B, when the cylinder 75 is in a position to close the outlets 312, 313, the front end of the cylinder 75 is located rearward of the outlet 312 in the in-shaft passage 31A. The refrigerant in the in-shaft passage 31A does not flow into the compression chamber 271 through the outlet 312. As shown in FIG. 9A, when the cylinder 75 is in a position to open the outlets 312, 313, the front end of the cylinder 75 is located frontward of the outlet 312 in the in-shaft passage 31A. The refrigerant in the in-shaft passage 31A is to flow into the compression chamber 271 through the outlet 312.

When the compressor 10 is in a stopped state, the cylinder 75 is retained at the disconnecting position shown in FIG. 9B by the spring force of the return spring 74. When the compressor 10 is started, the refrigerant in the inner space 317 (a part of the in-shaft passage 31A) between the front end of the cylinder 75 and the front end of the in-shaft passage 31A is introduced into the compression chamber 271, and the pressure in the inner space 317 is decreased. Thereby the cylinder 75 is shifted from the disconnecting position as shown in FIG. 9B to the connecting position as shown in FIG. 9A, overcoming the spring force of the return spring 74.

The valve body including the piston 69 and the cylinder 75 is shifted between the connecting position and the disconnecting position in accordance with the pressure in the inner space 317 (a part of the in-shaft passage 31A, or, the supply passage) corresponding to the operated state and the stopped state of the compressor 10. In the connecting position, the outlets 312, 313 in the supply passage are connected to the suction chamber 142 in the compressor 10. In the disconnecting position, the outlets 312, 313 in the supply passage are disconnected from the suction chamber 142.

According to the fifth preferred embodiment, the similar effects are obtained as the fourth preferred embodiment.

The following will describe a sixth preferred embodiment of the present invention with reference to FIG. 10. The same reference numerals denote the identical components to those in the first preferred embodiment.

The compressor housing assembly of the fixed displacement piston type compressor 10A includes a cylinder block 12, a front housing 13, and a rear housing 14. A crank chamber 24 is defined in the cylinder block 12 and the front housing 13 so as to accommodate a swash plate 23. Single-headed pistons 81 are engaged with the swash plate 23. The single-headed pistons 81 are reciprocated in cylinder bores 28 in accordance with the rotation of the swash plate 23. A rotary valve 36 is formed in a rotary shaft 21 at a position corresponding to the cylinder block 12. A valve body 42, a partition wall 48, a first bellows 51, a second bellows 52 are formed in the rear housing 14.

According to the sixth preferred embodiment, the similar effects are obtained as the first preferred embodiment.

The present invention is not limited to the above-described embodiments, but may be modified into the following alternative embodiments.

In the fifth embodiment, the bellows 51 of the first embodiment may be applied instead of the piston 69.

The first rotary valve 35 and the second rotary valve 36 may be formed independent from the rotary shaft 21.

The partition wall may be formed integrally with the rear housing (a part of the rear housing may serve as the partition wall).

Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims. 

1. A suction structure for allowing refrigerant into a suction pressure region in a fixed displacement piston type compressor, wherein cylinder bores for accommodating a respective piston are arranged around a rotary shaft, wherein a cam body is formed with the rotary shaft, wherein the piston is engaged with the cam body so that the rotation of the rotary shaft is transmitted to the piston, wherein a compression chamber is defined by the piston in the respective cylinder bore, wherein a rotary valve has a supply passage for introducing the refrigerant from the suction pressure region to the compression chamber, wherein the rotary valve is rotated integrally with the rotary shaft, the suction structure comprising: a shifting device for shifting between a connecting state and a disconnecting state, wherein in the connecting state the outlet of the supply passage is connected to the suction pressure region and in the disconnecting state the outlet of the supply passage is disconnected from the suction pressure region, the shifting device including; a valve body movable between a connecting position and a disconnecting position, wherein the connecting position corresponds to the connecting state and the disconnecting position corresponds to the disconnecting state; a return spring urging the valve body from the connecting position toward the disconnecting position; a first displacement chamber urging the valve body from the disconnecting position toward the connecting position, the volume of the first displacement chamber is displacable in accordance with an amount of a fluid inside therein; a second displacement chamber of which the volume is displacable, wherein the fluid is filled in the first and the second displacement chambers; and a throttle passage connecting the first displacement chamber to the second displacement chamber, wherein the volume of the first displacement chamber is increased when the fluid flows from the second displacement chamber to the first displacement chamber through the throttle passage, and wherein the volume of the first displacement chamber is decreased when the fluid flows from the first displacement chamber to the second displacement chamber through the throttle passage.
 2. The suction structure according to claim 1, wherein the first displacement chamber is formed between a partition wall and a first chamber forming member which has a first movable portion, wherein the second displacement chamber is formed between the partition wall and a second chamber forming member which has a second movable portion, wherein the throttle passage is formed so as to extend through the partition wall, wherein the volume of the first displacement chamber is displaced in accordance with the position displacement of the first movable portion, wherein the volume of the second displacement chamber is displaced in accordance with the position displacement of the second movable portion.
 3. The suction structure according to claim 2, wherein the first chamber forming member is a first bellows connected to the partition wall, and the second chamber forming member is a second bellows connected to the partition wall, wherein the first movable portion is a first movable end of the first bellows, wherein the second movable portion is a second movable end of the second bellows.
 4. The suction structure according to claim 3, wherein the valve body is fixed to the movable end of the first bellows.
 5. The suction structure according to claim 3, wherein the stroke length of the first movable end of the first bellows is greater than that of the second movable end of the second bellows when the displacement of the first bellows is the same magnitude as that of the second bellows.
 6. The suction structure according to claim 1, wherein the fluid is a liquid.
 7. The suction structure according to claim 1, wherein the valve body is located at the disconnecting position for disconnecting an inlet of the supply passage from the suction pressure region in the compressor when the shifting device is in the disconnecting state.
 8. The suction structure according to claim 1, wherein the supply passage includes an inlet at an end surface of the rotary valve and an outlet at an circumferential surface of the rotary valve, wherein the supply passage includes an in-shaft passage extending in the direction of the rotary axis of the rotary shaft, wherein the outlet of the supply passage is formed so as to extend through the circumferential surface of the rotary shaft and is connected to the in-shaft passage, wherein the valve body is slidably fitted in the in-shaft passage in the direction of the rotary axis, wherein the valve body is moved in the direction of the rotary axis between the connecting position and the disconnecting position, wherein in the disconnecting position the valve body disconnects the outlet of the supply passage from the in-shaft passage.
 9. The suction structure according to claim 1, wherein the compressor includes a cylinder block in which the cylinder bores are formed, wherein a rear housing is connected to the cylinder block, wherein a suction chamber as the suction pressure region is formed in the rear housing, wherein the valve body is provided in the rear housing.
 10. The suction structure according to claim 1, wherein the rotary shaft is connected to an external drive source through a clutch.
 11. A fixed displacement piston type compressor comprising: pistons; cylinder bores for accommodating the respective piston, wherein the cylinder bores are arranged around a rotary shaft; a cam body formed with the rotary shaft, wherein the piston is engaged with the cam body so that the rotation of the rotary shaft is transmitted to the piston; a compression chamber defined by the piston in the respective cylinder bore; a rotary valve including a supply passage for introducing refrigerant from a suction pressure region in the compressor to the compression chamber, wherein the rotary valve is rotated integrally with the rotary shaft; and a shifting device for shifting between a connecting state and a disconnecting state, wherein in the connecting state the outlet of the supply passage is connected to the suction pressure region and in the disconnecting state the outlet of the supply passage is disconnected from the suction pressure region, the shifting device including; a valve body movable between a connecting position and a disconnecting position, wherein the connecting position corresponds to the connecting state and the disconnecting position corresponds to the disconnecting state; a return spring urging the valve body from the connecting position toward the disconnecting position; a first displacement chamber urging the valve body from the disconnecting position toward the connecting position, the volume of the first displacement chamber is displacable in accordance with an amount of a fluid inside therein; a second displacement chamber of which the volume is displacable, wherein the fluid is filled in the first and the second displacement chambers; and a throttle passage connecting the first displacement chamber to the second displacement chamber, wherein the volume of the first displacement chamber is increased when the fluid flows from the second displacement chamber to the first displacement chamber through the throttle passage, and wherein the volume of the first displacement chamber is decreased when the fluid flows from the first displacement chamber to the second displacement chamber through the throttle passage. 